1. Field of the Invention
The present invention relates, in general, to an in-plane switching mode liquid crystal display device having a pixel electrode and a common electrode formed on the same substrate, and more particularly, to an in-plane switching mode liquid crystal display device capable of suppressing a liquid crystal polarization due to external static electricity to improve display image quality, by forming an induced electric field between a first conductive layer and a second conductive layer, to which a common voltage is applied through an electrical connection.
2. Description of the Related Art
In recent times, research on an in-plane switching mode (IPS) liquid crystal display (LCD) has been widely performed. The IPS LCD includes two electrodes formed on the same substrate such that a voltage is applied between the two electrodes to generate a horizontal electric field or a fringe electric field with respect to the substrate.
Hereinafter, the structure of a conventional IPS LCD will be described in brief with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of a conventional IPS LCD.
Since the conventional IPS LCD shown in FIG. 1 includes a pixel array 22 having a pixel electrode and a common electrode and formed at one side of a lower substrate 20, when static electricity is generated from an upper substrate having no electrode, a liquid crystal polarization may be generated in a liquid crystal layer (LC, 40) due to static electricity, thereby deteriorating display image quality. In order to prevent occurrence of the liquid crystal polarization, a method of grounding static electricity introduced from the exterior through an SUS bezel 30 upon introduction of the static electricity by coating a transparent conductive layer 16 on a rear surface of the upper substrate 10, and connecting a copper tape 32 to the SUS bezel 30 surrounding a mold frame 29 has been used.
As described above, the transparent conductive layer 16 in contact with the SUS bezel 30 functions as a ground terminal to prevent the upper substrate 10 as a dielectric material from being charged upon introduction of external static electricity, thereby preventing intrusion of the electric field into a liquid crystal 40 due to the static electricity.
However, when the SUS bezel 30 is removed in order to form a small, lightweight and compact device such as a mobile or portable appliance, the transparent conductive layer 16 formed on the rear surface of the upper substrate 10 must be floated, making it impossible to perfectly shield the static electricity.